In oil and gas operations, pressure pulses are often generated downhole. The pressure pulses can result from the operation of equipment such as valves or drilling equipment. The pressure pulses are useful for various functions, such as transmitting signals (e.g. MWD), activating equipment or improving drilling. For example, the applicant has proposed various arrangements for using pressure pulses to provide agitation of a downhole tubing string for a variety of purposes: see, for example, International Patent Applications PCT/GB2007/002553 and PCT/GB2004/004503, the disclosures of which are incorporated herein by reference.
To increase efficacy of the pressure pulses, it is generally desirable to use maximum pressure pulses. For example, for improved efficiency whilst drilling, it is often preferred to have an increased amplitude of pressure pulse to increase agitation. Similarly, an increased amplitude can help lengthen a distance over which a signal can be detectably transmitted, such as using MWD. However, an increased amplitude of pressure pulse can have a disadvantageous side-effect. For example, it is not always desirable to have both an increased distance over which a signal can be transmitted and an increased agitation.